I've used Duac for about two years as I found it to be more effective than the other topical treatments I've previously been given by my dermatologists, although that's not saying much as I've found my acne to be very persistent. I'm 27 and I've had it for around 10 years.

Duac has 5% benzoyl peroxide in it which has I believe been shown to be quite effective in treating acne. It also has an antibiotic in it (clindamycin) which can also help (although I am trying to avoid antibiotics in future as I've already been on some lengthy courses of oral erythromycin).

I found that Duac would sometimes stop my cysts becoming too large and inflamed, but it didn't stop them occurring and I recently gave up on it after having a breakout of several large cysts at once which have left me with a lot of hyperpigmentation. I'm now having a third course of (ro)accutane instead (although my second course was only a short one).

Having read this site I've realised that it may be my own fault that topical treatments have not been working properly - I've only been using a smallish amount on an area which already has a spot, whereas it seems you're supposed to treat the whole of your face whether it's currently affected or not (at least the areas which are spot prone) and to cleanse beforehand and moisturise afterwards using non-comedogenic products (which are quite hard to find in the UK in my experience).

So perhaps I'm not the best judge, but I found Duac to be moderately helpful but not a solution to my problems, at least not the way I was using it. For the first week or so it made my skin red and gave me a burning sensation but after that it worked fairly well for the limited purpose I was using it (i.e. killing existing spots), albeit quite slowly.

Once I get off roaccutane I'm going to start the regimen recommended here with the 2.5% benzoyl peroxide treatment, which is supposedly as effective as 5% BP but less drying. I can't recommend it yet but it seems to have received a lot of positive feedback here.